Poor Ground Research Articles

ON THE SETTLEMENT OF POOR COHESIVE SOIL GROUND CAUSED BY TUNNEL DRIVNG WITH SLURRY SHIELD MACHINE

This paper discusses the results of experiments on the settlements of poor cohesive soil ground caused by tunnel driving with a slurry shield. Driving tests were conducted with a slurry shield model having the diameter of 600 mm in the laboratory and an actual performance of slurry shielding was compared with the model test. The model tests show that there exists an optimum slurry pressure dependent on the overburden pressure and ground materials, and the ratio of the amount of soil to be excavated to that estimated from the shield diameter is nearly 96 to 97% for the optimum pressure. The field tests show that the optimum pressure is nearly equal to the pore pressure, and the optimum driving speed is such that soil at the face is kept in the region of somewhat passive condition. (Author abstract)

Improving poor ground

Improving poor ground

Les campagnes flamandes du XIIIe siècle au XVIIIe siècle, ou les succès d'une agriculture traditionnelle

Dans l'introduction qu'il a donnée à la réédition, en 1804, du Théâtre d'Agriculture d'Olivier de Serres, François de Neufchâteau relevait avec perspicacité, parmi d'autres causes, deux raisons pour lesquelles « les progrès de l'agriculture ont été si tardifs » : « La chimie, écrivait-il, qui promet beaucoup et qui tiendra parole, n'avait pas encore soumis à l'analyse les principes reproductifs des engrais naturels et artificiels » ; par ailleurs, « la mécanique, qui associe les forces de la nature à celle de l'homme, était encore loin de la perfection vers laquelle elle marche ».

Effects of Dried Sewage Sludge on Meadow Vole (Microtus pennsylvanicus) Populations in Two Grassland Communities

(1) Differences in meadow vole population densities were attributed to nutrient treatment effects on habitat quality; densities were low in communities with low plant species diversity and poor ground cover. (2) Survivorship was decreased in wheat field fertilized treatments, apparently due to poor vole habitat quality, although net primary production was significantly increased. (3) There was no evidence of toxic effects of sludge on vole population density, survival, or reproductive parameters. (4) Sex ratios favoured females in high food-quality habitats and males in low food-quality habitats.

OPTIMUM CROPPING AND GROUND WATER MANAGEMENT1

ABSTRACT: A decision model for optimum cropping pattern and ground water manaement alternatives in canal irrigated areas is pre sented. Various ground water management alternatives in conjunction with optimum cropping pattern and based on water production functions are compared. The model developed also ensures optimum utilization of surface and poor quality ground water and proper soil conditions for plant growth.

Two new methods of tunnelling through poor ground in built-up areas : Bougard, J F In: Tunnelling '79, Proceedings of the 2nd International Symposium, London, 12–16 March 1979, P216–219. Publ London: IMM, 1979

Two new methods of tunnelling through poor ground in built-up areas : Bougard, J F In: Tunnelling '79, Proceedings of the 2nd International Symposium, London, 12–16 March 1979, P216–219. Publ London: IMM, 1979

Reinforced earth structures situated on soft foundations

The authors investigate weaknesses in some current empirical design studies when used with structures situated on poor ground. Although it is theoretically possible to show that conventional earth retaining structures should be better suited to sites with poor bearing pressure capacity than reinforced earth structures, this is not generally the case in practical experience. A series of parametric studies using common material properties and an embankment height of 9 M have been undertaken using the program felsta to illustrate the properties of soft and very soft foundations. The effect of the width of the embankment or reinforced earth structure on overall stability is also investigated. It is concluded that the resistance to movement of the reinforced earth structure produced by the subsoil material radically alters the assumption that the structure will rotate forward about the toe. An expression for the stability of the structure is determined. Empirical design rules are only acceptable for narrow embankments. (TRRL)

A Design Method of Deep Excavation in Cohesive Soil Based on the Reliability Theory

ABSTRACT The recent excavation has become wider and deeper and in addition, the excavation works of poor ground have steadily increased. In design and construction of large-sized excavation works, the following two points are specifically important. One is the quantitative evaluation of various uncertainties which occur in design and construction. The other is the optimization of design and construction under consideration from the mechanical and economical aspects. In order to satisfy the two points, a design method based on the reliability theory is applied to the design of large-sized excavation works. In the first half of the present paper, the optimization of the prior design before construction is described. That is, the method to decide the optimal action in the prior design is discussed based on the statistical properties of soils and the analytical error of the conventional design equations. The obtained optimal solutions are compared with the actual results of the past construction fields. In the second half of this paper, the dynamic design procedure in which the results of the prior design are modified by new information obtained during construction is applied to the excavation problem. The dynamic design procedure which was firstly formulated for the embankment problem is modified so as to be applied to the excavation problem and the results obtained from the numerical studies are also compared with those actually obtained hitherto through the course of excavation works.

Fracture-Controlled Ground-Water Circulation and Well Siting in the Vicinity of Laramie, Wyoming.

The artesian Casper aquifer, comprised of 700 ft of interbedded limestones and sandstones, currently supplies 70 percent (3.5 Mgal/d) of the municipal-water needs of Laramie, Wyoming. Large transmissivities occur in fracture zones associated with faults and folds in the area, and water discharges from several springs localized along these structures. Transmissivities in fracture zones are 100 times greater than those in unfractured parts of the aquifer. The overlying Satanka Shale is a regional confining unit even in most areas of fracturing, and is a source of poor quality ground water. Prospecting for new ground-water supplies near Laramie involves mapping the tectonic structures and drilling into them once they are identified.

Foundations and earthworks for cylindrical steel storage tanks : Harris, G Ground Engng. V9, N5, July, 1976, P24–31

The design and construction techniques for steel storage tanks for storing oil and general bulk commodities are reviewed. The nature of storage tanks are described, the effects of settlement of tanks are discussed, and comments are made on tank loadings, foundations, water testing and settlement records, dyke compount areas, and underwriting considerations. Shell bearing plates are used for fixed roof tanks where shell bearing pressures are in excess of 100 kilopascals or where floating roof tanks are involved. Large size cone roof tanks have their roofs supported on columns and generally a center column. The dead load on columns normally ranges from 50 to 100 kn, whereas live load can add a further 100 to 150 kn per column. Foundation solutions for varying soil conditions are diagramatically illustrated and relate to shallow foundations in competant graound, foundations for poor ground conditions, fill replacement technique, piled foundations, and foundation preloading. Tests to ensure that the storage tank is water tight, and that the foundation is adequate to carry the loadings are discussed. The dyking (to retain spillage and prevent flooding and pollution) precaustions to be adopted in any instance will depend on the nature of the commodity being stored. Underwriting consideraions are discussed related to the storage of hydrocarbons.

Economical Evaluation of Embankment Design

The evaluation method of design of embankment is proposed on the basis of cost functions which are formulated in relation to its probability of failure. Four design alternatives are investigated. That is, (1) alternative A 1 is to increase the number of laboratory test in order to get more informations on soil properties, (2) alternative A 2 is to decrease the slope gradient, (3) alternative A 3 is to increase the resisting moment with a counter-weight fill and (4) alternative A 4 is to increase the shear strength by improving the poor ground with sand compaction piles. The proposed cost functions and the numerical examples show that the alternative A 4 gives the minimum total expected loss when the cost purchasing land is very expensive, but that the alternatives A 1, A 2 and A 3 tend to be selected for design when the land cost is not so expensive. Further, they show that the acceptable value of the failure probability for design should be reduced when the anticipated failure loss is considered very expensive.

Earthquake Hazard and Public Policy in California

Recent California laws on earthquake safety require the design engineer to consider some new concepts in his approaches to earthquake engineering design. In addition, he must broaden his design viewpoint to include closer working relationships with related disciplines. The policing of the design and construction of new hospitals has been pre-empted by the state from local control. The law now requires the engineer (both private consultants as well as government employed designers) to prepare designs of a type which will allow all future new hospitals to remain functional after an earthquake disaster. A second law implies that state approved dams are not automatically perfectly safe and therefore some acceptable degree of risk exists; as one result, downstream inundation maps must be prepared and released to the public. Two additional significant laws require land-use planning for the earthquake geologic hazards of faulting, structurally poor ground (such as marshes), and earthquake induced landslides; these laws do not preclude construction in these areas, but they will increase construction costs in some instances.

Tunnels for roads and motorways

Summary Geology is an important determinant affecting the planning, design and construction of a road tunnel. A road tunnel has to satisfy certain geometrical criteria and the achievement of the best economic route for a tunnel may be a complex operation, where the related geology offers any considerable choice. In this paper examples are given of the principal characteristics of three recent road tunnels in Britain, explaining the degree to which the wide variations in tunnelling cost depends upon the nature of the ground. It has generally been assumed that, where topography so allows, a road may be set underground by cut-and-cover construction at less cost than in a bored tunnel. In ground particularly favourable for economic tunnelling this is no longer necessarily true on direct engineering costs and, in an urban setting, other indirect costs tend to favour the case for a bored tunnel. Reference is made to the pattern of variations of cost with depth below surface for each of these types of tunnel. The site investigations for a tunnel should be designed to determine the properties of the ground relevant to the selection of tunnelling method and the estimation of constructional difficulties. A highly mechanised system of tunnelling is particularly sensitive to geological variation and calls for an appropriate effort to eliminate, within reasonable limits, the risk of encountering an insuperable or disproportionately costly difficulty. The problem of tunnel design relates directly to the competence of the ground. The concept of a competence factor is introduced in this respect. In soft ground, a principal problem is one of the adequacy of immediate support. In somewhat more competent ground, the extent of the need for immediate support depends on the knowledge of the stress/strain characteristics of the ground. For competent rock, the main problem concerns the means for determining the behaviour of the ground en masse. The method of excavation is also a factor affecting the behaviour of the rock around a tunnel. Over the last 15 years or so there has been considerable experience in the use of rock bolts and shotcrete in providing support to the rock as an alternative to more traditional methods. The behaviour of such expedients is discussed in relation to the nature of the rock and of its discontinuities. In soft ground, surface settlement may be important in determining the scheme for an urban tunnel. Settlement is not only largely dependent on the system of tunnelling but also upon the use of special expedients in relation to tunnelling in poor ground.

Visual Processing Training With the Tachistoscope

Diagnostic testing in kindergarten and the primary grades of children who are experiencing learning disabilities has revealed certain consistent perceptual deficiencies. Among these are poor figure ground relationships, poorly developed perceptual form constancy, inadequate spatial and directional relationships, immature visual motor development and finally, poor short term visual memory as measured with a tachistoscope. It is the purpose of this paper to establish a set of expected tachistoscopic responses using three digits at 0.1 and 0.01 seconds for children in the sixth month of grade one whose average age is six years, five months. Using a sample of 250 children, the mean, the median scores and a percentile scale have been developed so that a child in grades one, two or three who is experiencing a perceptual deficit can be compared to the grade one child. The coefficient of correlations between success in reading and tachistoscopic response at each speed has been calculated.

Visual Figure-Ground Discrimination in Patients With Unilateral Cerebral Disease

The purpose of this study was to evaluate the influence of aphasia, of visual field defects and the hemispheric side of the lesion on Gottschaldt Hidden Figure Test. This test was administered to 95 right handed patients with unilateral lesions of the cerebral hemispheres and to 40 control patients. The brain-damaged sample was divided into sub-groups according to the side of the lesion and the presence/absence of visual field defects and (within the left hemisphere group) of aphasia. Scores were compared by means of co-variance analyses, concomitant variables being age, years of schooling and visual reaction times (considered as a measure of the severity of the lesion). Il was found that visual field defects did not significantly affect the test scores. In contrast, poor performances were significantly associated with the presence and severity of aphasia. Right brain-damaged patients performed not differently from left brain-damaged patients, considered as one group. However, they did significantly worse than non-aphasic left brain-damaged patients. These were the only group whose mean score was virtually as good as that of the control group. These findings seem to indicate that poor visual figure ground discrimination (as tested by Gottschaldt test) in brain-damaged patients may be due to the impairment of at least two specific abilities, i.e. language (or some intellectual factor closely related to it) and some other ability (perhaps a visuo-spatial ability), preferentially subserved by the right hemisphere.

Effects of ground on shaking in earthquakes

Records of nearby earthquakes recorded simultaneously at the Seismological Laboratory, located on granite, and on the campus of the California Institute of Technology, located on alluvium, show that the first wave of a new phase frequently records with rather small differences at the two stations; however, if the following waves had periods of less than about two seconds they were recorded with appreciably larger amplitudes on the campus than at the Seismological Laboratory. Large amplitudes continued on the campus appreciably longer than at the Seismological Laboratory. Data available for locations on poor ground show that there the maximum amplitudes may be as much as ten times as large as those recorded at the Seismological Laboratory under otherwise equal conditions. Considering the importance of such results for engineering seismology it is intended to continue this research on a larger scale.

The Party System in Nova Scotia

The Nova Scotian party system was both a product of the struggle for responsible government and a major instrument in determining its outcome. While issues of some magnitude occasionally agitated the House of Assembly prior to 1835, none possessed such a character as to permit a clear-cut and continuing division of its members. In fact, whether the differences of those days were between Loyalist and pre-Loyalist, or between country and town, they usually sprang from no more than the struggle for personal advantage, and great public questions were lost sight of or did not arise. Up to the end of the Napoleonic wars Halifax had lived largely off the expenditures made by the British government. Hence before this flow of easy money dried up there was in Nova Scotia poor ground for the growth of a party in opposition to the oligarchy in which ecclesiastical, commercial, and political power was concentrated. Even when the first attacks upon this clique commenced in the 1820's, they were led for the most part by men of Tory sympathies who, while they felt free to make an occasional display of independence on specific constitutional issues, never carried it to the point where they might be labelled as confirmed critics of government.

British Forestry and the Development Commission

IT is more than two years since the Development Commission obtained its fine grant of 500,000l. yearly for five years. There have been Parliamentary grants in addition; thus 900,000l. was available the first year. Said The Times: “The Development Fund is a remarkable departure from the laissez-faire policy which has so long dominated the proceedings of British Governments.” It was early announced that one of the chief objects of the Development Commission was British forestry, including the purchase and planting of land. One small piece of poor ground in Scotland represents all the land that has yet been acquired in Britain; and foresters are beginning to inquire if we have really broken away from the bad traditions of the past. British forestry has never had such an opportunity as this half-million grant. Will anything practical be done before it is too late and the grant come to an end, because nothing practical has been achieved? It is true that there have been useful educational grants; and promises of loans for forestry, on liberal terms, to “local authorities or other responsible bodies”: but this, without State forestry, is putting the cart before the horse. As is well known, the communal forests on the Continent carry a class of forest inferior to the State forests, and they are only kept up to this standard by either State supervision or their management by State forest officers, combined with the stiffening effect of the better managed State forests in their midst.

Pocket Gophers of the United States

IN Bulletin No. 5 of the U.S. Department of Agriculture, Mr. Vernon Bailey gives an account of the habits and life-history of the Pocket Gophers of the United States, which contains a number of interesting facts and observations derived from various sources. These curious little rodents live underground in burrows which they tunnel in the soil. When working their way through the earth, they use the upper incisors as a pick to loosen the ground, while the fore-feet are armed with strong curved claws for digging. When a sufficient quantity of soil has accumulated behind an animal, he turns in the burrow and pushes it out in front until an opening in the tunnel is reached; the earth is here discharged, and forms a hillock similar to the hills thrown up by moles. Gopher burrows are extended and added to year by year, and the course is marked by the hills of soil brought up to the surface. Gophers do not hibernate, as has been commonly supposed, but work steadily throughout the winter. They do a great deal of good in mixing the soil, and in this way are probably most useful on poor or uncultivated ground. But, on the other hand, in agricultural districts the animals are highly injurious; they devour potatoes and other tubers and roots in large quantities, as well as corn, wheat, and other farm crops; and they destroy great numbers of fruit trees by gnawing off the roots. Gopher burrows also often do a great deal of damage in meadows or on the banks of artificial water-courses. So great is the harm done by Gophers, that in many districts bounties have been offered for their capture. One of the most striking features of Pocket Gophers is their possession of cheek pouches opening outside the mouth. It is commonly supposed that these pouches are used for carrying earth out of the burrows; but Mr. Bailey's investigations lead him unhesitatingly to the conclusion that this view is erroneous; they are used only for carrying food—pieces of potato and roots, leaves, &c.—to be eaten at ease in the seclusion of the animals— burrows, or to be stored up for use in the winter. The food is passed into the pouches by the forefeet; and the animals empty their pockets by pressing the sides of the head with the fore-feet from behind forwards, so that the contents fall out in front of them. In disposition Gophers are very fierce; and on the rare occasions on which they wander from their holes, frequently attack passers-by without any provocation. They are not very prolific animals, as is commonly stated, for only one litter of two or three young is produced in a year; but, although their rate of increase is slow, their mode of life protects them from many enemies which attack squirrels, mice, and many other rodents. The Pocket Gophers of the United States belong to three genera, Geomys, Cratogeomys, and Thomomys: Mr. Bailey gives two charts illustrating the distribution of these different genera and their constituent species.